1. Technical Field
The present invention relates to a support structure for a crankshaft rotatably supported on a cylinder block of an internal combustion engine.
2. Related Art
A crankshaft is rotatably supported on a cylinder block of an internal combustion engine (hereinafter, simply referred to as an engine), and the crankshaft is configured so that crank journals thereof are rotatably supported on a case of the cylinder block via sliding bearings (metal bearings).
An end portion of the crankshaft is arranged outside the case, and a sprocket connected to a cam shaft is attached on the end portion. Also, a pulley connected to auxiliary equipment, such as, an alternator, a power steering pump, an air conditioner compressor and the like is attached on the end portion of the crankshaft arranged outside the case.
Thus, a load from the cam shaft is intensively exerted on a region of the sliding bearing of the crank journal, which is located at the end side, through the chain and the sprocket, and also a load from the auxiliary equipment is exerted on the region of the sliding bearing of the crank journal, which is located at the end side, through the belt and the pulley.
As the auxiliary equipment attached to the engine, a starter generator constituted by combining a starter and a generator of the engine is known (see JP-A-2006-342694). The starter generator is an object larger than a general generator and is connected to the crankshaft of the engine via an auxiliary belt, such as a timing belt.
The engine having the starter generator is configured so that at startup, a driving force is inputted from the starter generator to the auxiliary belt and during operation of the engine, a driving force is inputted from the engine (crankshaft) to the auxiliary belt. In the engine having the starter generator, a particular large load is exerted on the auxiliary belt.
Accordingly, a large cantilever load from the auxiliary belt is exerted on the crank journal of the crankshaft, and thus there is a possibility that an oil film formation in the sliding bearing (metal bearing) is not facilitated so that friction loss and wear of the sliding bearing are increased.
Also, if alignment of the pulley around which the auxiliary belt is wound is not exactly performed, there is a possibility that friction is increased and a large load is exerted so that wear of the auxiliary belt is increased.
The present invention has been made keeping in mind the above problems, and an object thereof is to provide a support structure for a crankshaft according, which can reduce a load to be applied to the crankshaft from an auxiliary belt.